/// <summary>
/// Restores the device context to the specified state. The DC is restored by popping state information off a
/// stack created by earlier calls to the SaveHdc function.
/// The stack can contain the state information for several instances of the DC. If the state specified by the
/// specified parameter is not at the top of the stack, RestoreDC deletes all state information between the top
/// of the stack and the specified instance.
/// Specifies the saved state to be restored. If this parameter is positive, nSavedDC represents a specific
/// instance of the state to be restored. If this parameter is negative, nSavedDC represents an instance relative
/// to the current state. For example, -1 restores the most recently saved state.
/// See MSDN for more info.
/// </summary>
public void RestoreHdc()
{
#if TRACK_HDC
bool result =
#endif
// Note: Don't use the Hdc property here, it would force handle creation.
IntUnsafeNativeMethods.RestoreDC(new HandleRef(this, _hDC), -1);
#if TRACK_HDC
// Note: Winforms may call this method during app exit at which point the DC may have been finalized already causing this assert to popup.
Debug.WriteLine(DbgUtil.StackTraceToStr(string.Format("ret[0]=DC.RestoreHdc(hDc=0x{1:x8}, state={2})", result, unchecked ((int)_hDC), restoreState)));
#endif
Debug.Assert(_contextStack != null, "Someone is calling RestoreHdc() before SaveHdc()");
if (_contextStack != null)
{
GraphicsState g = (GraphicsState)_contextStack.Pop();
_hCurrentBmp = g.hBitmap;
_hCurrentBrush = g.hBrush;
_hCurrentPen = g.hPen;
_hCurrentFont = g.hFont;
}
#if OPTIMIZED_MEASUREMENTDC
// in this case, GDI will copy back the previously saved font into the DC.
// we dont actually know what the font is in our measurement DC so
// we need to clear it off.
MeasurementDCInfo.ResetIfIsMeasurementDC(_hDC);
#endif
}
/// <summary>
/// Saves the current state of the device context by copying data describing selected objects and graphic
/// modes (such as the bitmap, brush, palette, font, pen, region, drawing mode, and mapping mode) to a
/// context stack.
/// The SaveDC function can be used any number of times to save any number of instances of the DC state.
/// A saved state can be restored by using the RestoreHdc method.
/// See MSDN for more details.
/// </summary>
public int SaveHdc()
{
HandleRef hdc = new HandleRef(this, _hDC);
int state = IntUnsafeNativeMethods.SaveDC(hdc);
if (_contextStack == null)
{
_contextStack = new Stack();
}
GraphicsState g = new GraphicsState();
g.hBitmap = _hCurrentBmp;
g.hBrush = _hCurrentBrush;
g.hPen = _hCurrentPen;
g.hFont = _hCurrentFont;
_contextStack.Push(g);
#if TRACK_HDC
Debug.WriteLine(DbgUtil.StackTraceToStr(string.Format("state[0]=DC.SaveHdc(hDc=0x{1:x8})", state, unchecked ((int)_hDC))));
#endif
return(state);
}
/// <include file='doc\IDeviceContext.uex' path='docs/doc[@for="DeviceContext.Dispose1"]/*' />
internal void Dispose(bool disposing)
{
if (_disposed)
{
return;
}
if (Disposing != null)
{
Disposing(this, EventArgs.Empty);
}
_disposed = true;
switch (_dcType)
{
case DeviceContextType.Display:
Debug.Assert(disposing, "WARNING: Finalizing a Display DeviceContext.\r\nReleaseDC may fail when not called from the same thread GetDC was called from.");
((IDeviceContext)this).ReleaseHdc();
break;
case DeviceContextType.Information:
case DeviceContextType.NamedDevice:
// CreateDC and CreateIC add an HDC handle to the HandleCollector; to remove it properly we need
// to call DeleteHDC.
#if TRACK_HDC
Debug.WriteLine(DbgUtil.StackTraceToStr(String.Format("DC.DeleteHDC(hdc=0x{0:x8})", unchecked ((int)_hDC))));
#endif
IntUnsafeNativeMethods.DeleteHDC(new HandleRef(this, _hDC));
_hDC = IntPtr.Zero;
break;
case DeviceContextType.Memory:
// CreatCompatibleDC adds a GDI handle to HandleCollector, to remove it properly we need to call
// DeleteDC.
#if TRACK_HDC
Debug.WriteLine(DbgUtil.StackTraceToStr(String.Format("DC.DeleteDC(hdc=0x{0:x8})", unchecked ((int)_hDC))));
#endif
IntUnsafeNativeMethods.DeleteDC(new HandleRef(this, _hDC));
_hDC = IntPtr.Zero;
break;
// case DeviceContextType.Metafile: - not yet supported.
case DeviceContextType.Unknown:
default:
return;
// do nothing, the hdc is not owned by this object.
// in this case it is ok if disposed throught finalization.
}
DbgUtil.AssertFinalization(this, disposing);
}
/// <summary>
/// Constructor to construct a DeviceContext object from an existing Win32 device context handle.
/// </summary>
private DeviceContext(IntPtr hDC, DeviceContextType dcType)
{
_hDC = hDC;
_dcType = dcType;
CacheInitialState();
DeviceContexts.AddDeviceContext(this);
#if TRACK_HDC
Debug.WriteLine(DbgUtil.StackTraceToStr($"DeviceContext(hDC=0x{(int)hDC:X8}, Type={dcType})"));
#endif
}
/// <summary>
/// Constructor to construct a DeviceContext object from an window handle.
/// </summary>
private DeviceContext(IntPtr hWnd)
{
_hWnd = hWnd;
_dcType = DeviceContextType.Display;
DeviceContexts.AddDeviceContext(this);
// the hDc will be created on demand.
#if TRACK_HDC
Debug.WriteLine(DbgUtil.StackTraceToStr(string.Format("DeviceContext( hWnd=0x{0:x8} )", unchecked ((int)hWnd))));
#endif
}
///<summary>
/// If the object was created from a DC, this object doesn't 'own' the dc so we just ignore this call.
///</summary>
void IDeviceContext.ReleaseHdc()
{
if (_hDC != IntPtr.Zero && _dcType == DeviceContextType.Display)
{
#if TRACK_HDC
int retVal =
#endif
IntUnsafeNativeMethods.ReleaseDC(new HandleRef(this, _hWnd), new HandleRef(this, _hDC));
// Note: retVal == 0 means it was not released but doesn't necessarily means an error; class or private DCs are never released.
#if TRACK_HDC
Debug.WriteLine(DbgUtil.StackTraceToStr(string.Format("[ret={0}]=DC.ReleaseDC(hDc=0x{1:x8}, hWnd=0x{2:x8})", retVal, unchecked ((int)_hDC), unchecked ((int)_hWnd))));
#endif
_hDC = IntPtr.Zero;
}
}
/// <summary>
/// Explicit interface method implementation to hide them a bit for usability reasons so the object is seen as
/// a wrapper around an hdc that is always available, and for performance reasons since it caches the hdc if
/// used in this way.
/// </summary>
IntPtr IDeviceContext.GetHdc()
{
if (_hDC == IntPtr.Zero)
{
Debug.Assert(_dcType == DeviceContextType.Display, "Calling GetDC from a non display/window device.");
// Note: for common DCs, GetDC assigns default attributes to the DC each time it is retrieved.
// For example, the default font is System.
_hDC = IntUnsafeNativeMethods.GetDC(new HandleRef(this, _hWnd));
#if TRACK_HDC
Debug.WriteLine(DbgUtil.StackTraceToStr(string.Format("hdc[0x{0:x8}]=DC.GetHdc(hWnd=0x{1:x8})", unchecked ((int)_hDC), unchecked ((int)_hWnd))));
#endif
}
return(_hDC);
}
/// <summary>
/// Constructor to construct a DeviceContext object from an existing Win32 device context handle.
/// </summary>
private DeviceContext(IntPtr hDC, DeviceContextType dcType)
{
_hDC = hDC;
_dcType = dcType;
CacheInitialState();
DeviceContexts.AddDeviceContext(this);
if (dcType == DeviceContextType.Display)
{
_hWnd = IntUnsafeNativeMethods.WindowFromDC(new HandleRef(this, _hDC));
}
#if TRACK_HDC
Debug.WriteLine(DbgUtil.StackTraceToStr(string.Format("DeviceContext( hDC=0x{0:X8}, Type={1} )", unchecked ((int)hDC), dcType)));
#endif
}
/// <summary>
/// Constructor to construct a DeviceContext object from an existing Win32 device context handle.
/// </summary>
private DeviceContext(IntPtr hDC, DeviceContextType dcType)
{
_hDC = hDC;
_dcType = dcType;
CacheInitialState();
DeviceContexts.AddDeviceContext(this);
if (dcType == DeviceContextType.Display)
{
_hWnd = Interop.User32.WindowFromDC(new HandleRef(this, _hDC));
}
#if TRACK_HDC
Debug.WriteLine(DbgUtil.StackTraceToStr($"DeviceContext(hDC=0x{(int)hDC:X8}, Type={dcType})"));
#endif
}
